In recent years, use of mobile communications devices for voice telephone services, email or text messaging services and even multi-media services has become commonplace, among mobile professionals and throughout the more general consumer population. To support broad customer's efficient acquisition of mobile communication networks, many mobile devices today are capable of using various networks and even different network technologies in many different regions, and increasingly, in different countries.
For the efficient acquisition of mobile communication networks, the carriers and their equipment vendors have developed and standardized a number of techniques for selecting systems in different areas for acquiring the network and obtaining service therefrom, in accordance with preferences of the subscriber's service provider/carrier. However, since the 3GPP2 and 3GPP standards bodies are working independently, the system selection procedures that they have established are different and use databases that are structured differently. 3GGP2 uses a Preferred Roaming List (PRL) that contains a table which identifies all of the operators that are roaming partners and which lists those partner operators in priority order. 3GPP uses Public Land Mobile Network (PLMN) lists to do the same.
Searching and acquiring a network, using a full PRL or PLMN search, however, takes considerable time and is typically done when a device is first turned-on or has lost all network service for some period of time. Each network listing in a typical preference list, e.g. in a PRL, might include a system ID (SID), a network ID (NID), a channel identification, and identification of a Radio Frequency Band, for each system and be classified by a geographic information index. The search may be time consuming, especially if a system has one or more configurable system parameters, and each such parameter can have one of multiple possible values. In this case, the station may perform acquisition for different possible combinations of values for the configurable system parameters in order to detect the system. Search and acquisition for a large number of possible combinations of parameter values from a long PRL or PLMN may extend search time and consume excessive battery power, both of which are undesirable.
For faster acquisition in other cases, for example, when the mobile device has been powered off briefly or in some cases when the device disconnects from one system while roaming, the device normally searches using a Most Recently Used (MRU) list having information of some much smaller number the most recently connected systems. The MRU list includes modes (CDMA, AMPS, EV-DO, etc.), band classes (Cellular, PCS, etc.) and channels of the most recently used systems. When an network is not found that matches a listing in the MRU list, the mobile device may turn to a more extensive search based on the PRL or PLMN. In this later case, if the device selects a new system, the device adds the system as a new entry in the MRU list for future use.
In this fashion, the MRU data is compiled over time from systems selected based on the carrier's preference list (PRL or PLMN). The preferences and thus the list or lists may change over time, as the carrier changes. To update the preference functionality of the devices of the carrier's customers, updated versions of the PRL or PLMN are provided to the mobile station over the air from time to time by the wireless communication provider. When a PRL is sent to a mobile device, the device does not use the new version until complete loss of signal or catastrophic power loss. Hence, as a result of an update, the acquisition data for one or more systems listed in the MRU may no longer conform to the carrier's latest preferences. In addition, the MRU can become swayed to one channel over the preferred channel due to channel assignment. Selection of such a system via the MRU, therefore, may no longer result in the most favorable financial roaming treatment.
Hence a need exists for technology to correct any discrepancies between the system identifiers captured in the MRU and those in the latest system preference list (e.g. PRL or PLMN) received from the carrier.